The present invention relates to a reduced pressure backflow preventor valve assembly and in particular to a backflow preventor having a relatively short length.
Backflow preventors are generally provided for allowing flow of water (or other fluid) from a source (such as a city water source) into a service location (such as a building) and ultimately to a use location. The backflow preventor valve, however, prevents flow of a fluid in the opposite direction (e.g., for avoiding contamination of a city potable water supply, and the like). A number of configurations can be used for avoiding backflow including a vacuum breaker system and a double check valve system. In many situations, municipal building codes and the like require use of a double check valve system. In a double check valve system, the fluid, in normal use, flows through the (normally open) first valve, into a zone between the two check valves and then flows through the (normally open) second check valve. A relief valve coupled to the zone is normally closed. During normal use, the zone is maintained at a pressure lower than the inlet pressure. In general, if there is a pressure at the outlet which is not at least a predetermined amount lower than the pressure at the inlet, the check valves will close, preventing backflow. If abnormal conditions arise, in which there is no flow, or reversal of flow, and the second check valve is in a failed state, the differential release valve will open and discharge to maintain the zone at a pressure lower than the supply. When normal flow resumes, the zone""s differential pressure will resume and the relief valve will close.
Backflow preventor valves are commonly used (and often required) at a service connection, such as the connection from a city water supply to a building water inlet. Often, such service connection backflow preventors must accommodate relatively high pressures (such as about 250 psi or more) and typically provide backflow prevention for relatively large-diameter fluid lines such as substantially greater than one inch inside diameter fluid lines.
In some situations, relatively smaller backflow preventor assemblies are called for. For example, point of use backflow preventors, which typically connect a water (or other fluid) use station to conduits within a building (e.g., as opposed to a service connection, directly connecting to a building water supply) are often relatively lower pressure (such as less than about 200 psi, often less than about 150 psi) and relatively smaller diameter (such as about one inch or less inside diameter, often three-quarter inch or less, or one-half inch or less). Non-exhaustive examples of point-of-use applications for backflow preventors include assemblies used to protect against high hazard (toxic) fluids in, e.g., beverage dispensers, industrial plants, hospitals, dental offices, morgues, mortuaries, chemical plants, irrigation systems, boiler feed and the like.
Some previous approaches to point of use backflow preventors are believed to have represented merely scaled-down versions of service connection (or other relatively large) backflow prevention assemblies. It is believed that previous approaches have not generally taken advantage of the opportunities presented by the fact that the devices are relatively low-pressure, low-diameter applications and, at least partially as a result, previous devices have tended to be undesirably large (including undesirably long, i.e., measured from the plane of the inlet opening to the plane of the outlet opening) heavy, and expensive to design, install, repair, maintain and/or replace. In addition, the relatively large size of previous approaches has made it infeasible to install such devices in relatively small spaces or volumes. Accordingly, it would be useful to provide a double check valve backflow preventor assembly having a relatively small size (including small length and/or small volume), lightweight and low-cost compared to typical previous backflow prevention assemblies, particularly previous small-diameter/low-pressure devices.
Many previous backflow preventors are configured with inlet and outlet openings which are substantially non-parallel and/or non-coaxial and/or provide flow in opposite directions with respect to one another. In many applications, this means that additional fittings are required for installation in an in-line situation (which is common in point-of-use applications) undesirably adding to the cost of design, installation, maintenance and the like, as well as potentially increasing the size or volume of the device as installed. Accordingly, it would be useful to provide a backflow prevention assembly with inlet and outlet openings which are parallel, preferably coaxial and define flow in the same direction with respect to one another.
Many previous backflow preventors are configured such that servicing, repair maintenance and the like is performed in a plurality of positions or directions (such as providing top or front access to a first valve and bottom or rear access to second valve, and the like). Such a configuration is believed to be inconvenient in many situations, especially in point of use applications where the available space or volume for accommodating access to a backflow preventor for maintenance and the like is typically severely limited. Accordingly, it would be useful to provide a backflow preventor assembly in which a plurality of components, and preferably at least both check valves, can be accessed for repair or maintenance from a single location or direction.
In addition, a backflow preventor assembly generally includes (an often is required, by code, to include) an upstream stop valve and downstream stop valve. Such stop valves can be used, e.g., for shutting-off flow in the event of failure of the check valves and/or relief valve or for facilitating maintenance or repair operations. Accordingly, a typical reduced pressure, double check valve backflow preventor assembly will include first and second check valves, first and second stop valves and a relief valve.
In many previous backflow prevention assemblies, at least some of the components were provided having a separate housing or enclosure, thus requiring installation of bolts through flanges or other coupling devices in order to achieve the desired total assembly. Such coupling devices typically add to the volume, length and/or weight of the total assembly. Accordingly, it would be useful to provide a backflow prevention assembly in which substantially all components, preferably including at least first and second check valves, first and second stop valves and a relief valve, are substantially enclosed using a single housing without the need for a coupling device.
Many previous check valve assemblies provided for installation or removal of some or all constituent components using devices which generally require hand and/or power tools (such as wrenches, screwdrivers, nutdrivers and the like), typically involving inserting or removing bolts, nuts, screws and the like. Without wishing to be bound by any theory, it is believed that this type of assembly/disassembly approach was provided for accommodating or withstanding the forces and pressures found in typical high pressure service connection devices. In general, it is believed that assembly devices and procedures which require the use of tools can lead to relatively high costs of fabrication, assembly, maintenance and repair of backflow prevention assemblies, and may be infeasible in situations where the room volume which is available for accommodating tools and the like is limited (e.g., as is common for point of use applications). Accordingly, it would be useful to provide a backflow prevention assembly which can, compared to previous approaches, reduce the number of components requiring tools for fabrication, assembly, disassembly service, maintenance repair and the like such as by providing at least some components which are readily assembled by hand (without the need for tools).
The present invention includes a recognition of the existence, nature and/or source of problems in previous approaches, including as described herein.
In one aspect, the present invention provides an in-line, reduced-pressure double check valve backflow preventor assembly with first and second serial check valves having valve movement axes which are both positioned substantially greater than 45xc2x0, preferably about 90xc2x0 to the in-line axis. The in-line axis lies along the substantially coaxial inflow and outflow directions of the assembly. Preferably, each of the movement axes of the two check valves substantially intersect (and are preferably substantially perpendicular to) the in-line axis. In one aspect, the first and second check valves are positioned such that the direction of flow through the first check valve is substantially parallel to, but opposite in sense, to the direction of flow through the second check valve. In one aspect, a relief valve defines a longitudinal axis which does not intersect the in-line axis and is preferably substantially parallel to, but offset from, a plane common to the axes of the two check valves. In one embodiment, first and second shutoff valves, which are preferably ball valves, are positioned in a common housing with at least the first and second check valves, and are preferably positioned on the in-line axis. In one embodiment, a double check valve, reduced-pressure backflow preventor assembly, including a relief valve with integrated shutoff valves connectable, in-line, to one-half inch inlet and outlet conduits, and having a maximum working pressure of about 150 psi has a length (distance between plane of the inlet opening and the plane of the outlet opening) less than about 200 millimeters, preferably less than about 195 millimeters even more preferably less than about 185 millimeters, and a weight less than about 2 kilograms, preferably less than about 1.8 kilograms. Preferably, the assembly has a head loss of less than about 22 psi at a flow of about 10 gallons per minute.
In one aspect, a double check valve reduced pressure backflow preventor assembly is configured to have a relatively small length, volume and/or weight. The assembly defines parallel, preferably coaxial, inlet and outlet directions. In one aspect, first and second check valves are at an angle, preferably of 90xc2x0, to the in-line axis and preferably intersect, the in-line axis. In one aspect, a relief valve is positioned spaced from the in-line axis. First and second shutoff valves are enclosed in the same integral, unitary housing which encloses the check valves and, preferably, some or all of the relief valve. The shutoff valves are preferably positioned along the in-line axis.